spark plug NGK IFR5A11 or Denso SK16R11?

I just replaced my spark plugs in my 2006 Prius with 170K miles. It's been a little over 40K miles since they were last replaced. Compared to the first pic I posted above, the plugs are getting progressively worse. I did use anti-seize on these plugs, perhaps one of the reasons they look the way they do? Also, it appeared there was oil around the spark plugs where they tighten on the block, could this be the valve cover gasket needing replacement?

 

for an engine with 170k miles, those plugs look pretty good

 

The third from the left definitely looks a bit oily. Just wondering, what is your oil consumption like at this stage?

 

It's hard to gauge my oil consumption because I change my oil twice a month. I never add oil in between changes. I use Toyota OEM filters and Mobile 1 5W-30 High Mileage Synthetic Motor Oil.

 

twice a month? That's 10,000 miles a month of driving.

 

I put 40K miles on this car last year. I did take a trip to CA, I had the oil changed at a dealership in Hanford. I did have to add oil on the return trip. I look at it this way. I can take my car to the dealership and have the oil changed using synthetic motor oil for $85 each time or change the oil twice a month myself for $67 total.

 

You can go 10k miles with a synthetic oil change or 5k miles with a conventional oil change. So if you were to go 40k miles a year, that would only require oil changes done at 5k mile intervals.

These engines burn oil at high mileage, so I would pay close attention to how much oil the car is using, just so you don't run dry.

 

The main reason that I change the oil so often is because it seems to get dirty quickly.

 

I understand that these spark plugs only have 40K miles of service. If that is the case, they don't look very good, especially the one plug that has a fouled tip.

Did you use a torque wrench when installing these plugs, and tighten to the correct spec (13 ft.-lb)? If not, maybe the plugs were too loose, allowing HC deposits to leak out via the threads and deposit on the spark plug body.

I would have the engine compression checked if this were my car.

 

Patrick, I didn't use a torque wrench when installing this set of plugs, but they were not loose when I removed them. The plug in the picture, second from the left, was hard to remove, most likely due to the use of anti-seize on the threads. When installing the plugs I always hand tighten them before snugging them with a wrench. I'm thinking that the reason these plugs look this way has a lot to do with the mileage that I put on this car over the last year. 40K miles in 1 year is a lot of miles. This is mainly city driving over different types of terrain. I have always changed the oil in the car a MINIMUM of 1 time per month since purchasing it in March of 2010. I also use a magnetic drain plug. I think the condition of the plugs reflects the amount of wear and tear that I have put on this car over the last year. I may wind up selling the car shortly, but may just keep it as my business car for now. The car still serves its purpose without issue.

 

Just to add a data point on the spark plug conversation: I just changed plugs last week at 119k - the NGK originals were still in spec - the gap on all four plugs was the same as the Denso plugs that I used as the replacements.

Also, I change oil every 5k and no oil consumption between changes so far with Mobil 1 5W30

 

Up here our dealership sells Toyota 0W20 bottled liters for $5.91 (Canadian), bulk liters (my choice) for $4.50 per liter.

 

Any updates on your plugs or Oil consumption?

Also noticed your switch from standard to synthetic, was there a reason?

 

There is definitely reason for using good synthetic oil..especially the way this engines operate

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Unless you are towing, driving on dirt roads 50% of the time or leaving your car running all day like a taxi or a cop, then there is no reason to change your oil before the Maintenance light comes on at 5000 miles and is really just warning you to do it soon, so the real intention by the manufacturer is 6000 miles for regular oil. If you use synthetic than you can go longer. Changing it sooner is just throwing money and time away. The car will die from something else long before oil induced engine failure.
I didn't change the original NGK IFR5A11 plugs until 155,000 miles and they still worked fine, but were rough looking. I replaced them with NGK IFR5T11 plugs which are the OEM replacement suggested on the NGK website ( PEP boys carries them) as the IFR5A11 plugs were not available. So far I don't see any mileage difference. I would not suggest changing them before 100,000 miles.

 

I believe the plugs you bought won't go 100,000 miles, rated for only 60,000 miles. But the OEM ones from NGK would go 120,000+

 

I recognize this is an old thread, but I just happened across it and wanted to provide a bit of input in case anyone else had a similar experience with the "coloring" on those plugs. The brownish coloring on the porcelain directly above the hex is indicative of this style plug NOT being properly torqued. Although many automobile manufacturers have recommended torque values, most spark plugs that use a crush washer also have their own torque requirements to ensure proper seal. Many of them have the torque requirement printed on the box it's packaged in.

 

My personal preference is NGK. I remember replacing the plugs on a Tacoma TRD that had the factory plugs still. It was the V6 5VZ-FE engine with coil packs on one side and wires going from the coil packs to the cylinders on the other side. Weird setup that fired 2 times per cycle. The coil pack side used NGK,s. The plug wire side used Denso’s. Always figured the factory put more faith in the NGK’s. They had the harder life on the coil pack side.